Modelling infragravity waves and currents across a fringing coral reef

Conference paper (2012)

Authors

AR van Dongeren Deltares

Ryan J. Lowe University of Western Australia

Andrew Pomeroy University of Western Australia, Deltares

Duong Minh Trang IHE Delft Institute for Water Education, Deltares

D. Roelvink IHE Delft Institute for Water Education, Coastal Engineering - , Deltares

Graham Symonds Oceans and Atmosphere

Roshanka Ranasinghe IHE Delft Institute for Water Education, Coastal Engineering - , Deltares

Research Group

Coastal Engineering () (TU Delft)

Hydrodynamics XBeach Infragravity waves Fringing coral reefs Wave breaking Low frequency waves Surfbeat

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Published Date

2012

Language

English

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Faculty

Civil Engineering & Geosciences

Department

Hydraulic Engineering

Research Group

Coastal Engineering

Abstract

Low-frequency (infragravity) wave dynamics on a fringing coral reef were investigated using the numerical model XBeach (Roelvink et al, 2009). First, the skill of the one-dimensional model was evaluated based on its predictions of short waves (0.04-0.2 Hz), infragravity waves (0.004-0.04 Hz) and water level measurements (tidal elevation and wave setup) obtained during a 2009 field study at Ningaloo Reef in Western Australia. The model calibration was sensitive to friction coefficients for short waves and current / infragravity bed friction, which were assumed independent in this model study. The infragravity waves were found to be generated primarily in the surf zone through the breakpoint generation mechanism rather than through offshore forcing. The infragravity waves were also strongly modulated over the reef by tidal depth variations, primarily due to the variability in frictional dissipation rates when the total water depth over the reef varied. The results revealed that short waves dominated bottom stresses on the forereef and near the reef crest; however, inside the lagoon, infragravity waves become increasingly dominant, accounting up to 50% of the combined bottom stresses.